Electric motor controlling apparatus



Aug. 19, 1947. E. w. KUHN 2,426,029

ELECTRIC MOTOR CONTROLLING APPARATUS Filed Aug. 10, 1945 2 Sheets-Sheet 1 .96 WITNESS 6/ INVENTOR &a f [dmunoh/A uhn W I BY g ATTORNEY E. W. KUHN ELECTRIC MOTOR CONTROLLING APPARATUS Filed Aug. 10, 1945 2 sheets sheet 2 a h m n E o w d w 9 F/ r m8 PC 4 5 F 2 E o W A 3 m 7 r m i 3 9 rwm 4 e 7 my w @w a 9 2 4 L 4 0 nu V. a L H, m 8% Q 9 i ii w m N 7 5 =5 w 6B 6 n Hum p i m l fi/ 7 4 6 w Patented Aug. 19, 1947 entice ELECTRKC @QNTRQLLENG APZAEATUS Edmund W. Kuhn, Cortland, Qhio, assignor to Westinghouse Electric @orporation, East Pittsburgh, Pa, a corporation of Pennsylvania Application August it, 1945, Serial No. 610,101

7 Claims. i

This invention relates to electrical apparatus and particularly to circuit controlling apparatus for effecting the sudden stopping of an electric motor upon interruption of the circuit supplying the energizing current for operating the motor.

in many types of apparatus such as tar changing voltage regulators, machine tools and welding equipment, electrical mechanism is op erated by a motor that is required to operate high speed followed by a rapid deceleration of the motor speed to rest within a limited number of revolutions upon interruption of the motor circuit. In certain types oi such electrical appa ratus, it is customary to provide a braking mech anism of the friction type for stopping the motor and the operating mechanism associated therewith promptly upon the interruption of the Inc-- tor driving circuit. Such braking mechanism is usually provided with biasing means for normally maintaining the brakes applied when the motor is deenerg'ized and with electrically energized releasing means that is operated upon the ener gization of the motor to release the brakes,

is well .znown that amotor may be braked dynamically by reversing the connection of its leads .to the power source to efi'ect the supply of energy to the motor from the source in a dlrection to create a motor torque in the reverse direction to its direction of rotation. This operation is commonly terminated plugging the motor. Certain clifficulties occur in plugging the motor of the small size customarily employed in voltage regulators or similar equipment because the inertia of the moving parts is so small that the duration of time during which the reverse direction of power is required to be applied to l the motor to bring it to a complete stop without reversing the direction of operation of the motor is very short.

it is an object of my invention to provide means for stopping a motor by supplying power thereto in a direction to reverse the motor torque and for interrupting th current supplied to of. feet such a reverse motor torque upon the stopping of the motor.

Other objects and advantages of my invention will be apparent from the following description of a preferred embodiment thereof, reference being had to the accompanying drawing, in which:

Figure l is a diagrammatic View of apparatus and circuits illustrating an application of the invention to a tap-changingregulating trans-- former.

Fig. an elevational view of a directional and it that are inductively related to secondary through which energy is supplied to the three-phase circuit represented by secondary conductors ll, l2 and i3. A tapchanging mechanism is provided for varying the V voltage ratio between the ductors i, 2 and 3 and the 'econdary circuit contact members it in each of the three phases that are similarly operated by mechanism illustrated as an arm iii controlled by a screw threaded shaft ii that is operated through suitable mechanical means by a motor 6 9. I

Control equipment for the tap-changing mechanism is provided comprising a circuit controller or primary relay 2t having a pivoted arm 2i and an armature-controlled by an operating winding that is connected to be energized from a transformer winding 25% that is a measure of the quan tity to be regulated. The primary relay Ell controls the secondary relays 29 and 24 power from the transformer winding motor it to effect operation of the motor in the one or the other direction to maintain the desired voltage on the power circuit ll, l2 and 93. A directional switch device '25 which may be rotation of the motor shaft it.

If the voltage of the secondary circuit drops below the desired value, the energization of the primary relay winding 22 is decreased permitting the armature to drop and the movable contact member to engage the contact member 28 to complete a circuit from the transformer winding 25 through conductor 3 l, contact members 27 and the windings of the relay and conplalned, closing a preset ing the motor- I9 to operate in a direction to effect an operation of the tap-changing mechanism to cause an increase in the voltage on the secondary conductors II, I2, I3. Upon operation of the motor I9, switch contact members 4| of the directional switch device 25 are brought into engagement in a manner to be later excircuit including conductor 42, conductor 43, to the motor terminal 44 through the motor winding 45, terminal 35 and conductor 31, which preset circuit will be completed upon the deenergization of the relay 29 causing the relay contact member 45 to drop to its illustrated position closing the preset circult through the relay contact members 41. This preset circuit supplies energy to the motor I9 causing it to develop a torque counter to its direction of rotation, thus rapidly bringing the motor I9 to a stop.

Upon the stopping of the motor I9, the switch contact members 4| are operated to interrupt the preset or "plugging" circuit so as to prevent operation of the motor in the reverse direction.

If the voltage of the secondary circuit II, I2, I3 increases above the desired value, the relay 28 operates causing the contact member 21 to engage the contact member 49, thus closing a circult through the winding 49 of the secondary relay 24 causing the relay contact member 5| to move upwardly and engage the contact members 52, closing a circuit from conductor 3|, contacts 52 through conductor 53, motor terminal 44, motor winding 45, motor terminal 35 and conductor 31 to cause the motor I9 to operate in'a direction to operate the tap'changing mechanism to decrease the voltage of the secondary circuit represented by conductors II, I2 and I3. When the motor I9 is operated to increase the secondary circuit voltage, switch contact members 54 of the directional switch device 25 are operated into circuit closing relation to close a preset motor plugging circuit that will be effective when the relay contact member 5| drops to its lower position to engage lower switch contact members 55. This circuit extends from.

conductor 3| through relay contact members 5| and 55, conductor 55, switch contact members 54, conductor 51, to the motor terminal 34, motor winding 35, motor terminal 36 and conductor 31 to the transformer winding 25. When the voltage on the secondary circuit conductors II, I2 and I3 has reached the desired value, the relay 28 will operate to separate contact members 21 and 48, deenergizing the secondary relay 24 and causing the relay contact member 5| to drop to its lower or illustrated position, interrupting the motor energizing circuit and completing the above traced motor plugging circuit through the secondary relay contact members and directional switch contact members 54, thus applying a torque to the motor I9 in a direction reverse to its direction of operation bringing the motor to a quick stop. When the motor is brought to a stop, the directional switch device contact members 54 are separated, placing the mechanism in condition for further operation in accordance with operation of the primary relay 29.

Referring to Figs. 2, 3, 4, switch device is illustrated that is effective for closing the preset motor plugging circuit. A frame consisting of a sidewall 58 and bottom wall 8| is provided for supporting parts of the directional switch device. A control shaft 53 is provided and is keyed as shown at 54 "to the motor shaft I5 or a shaft driven in accordance with the direction and speed of operation of the motor l9. A brake drum 55 is provided on the inner end of the control shaft 59 and is engaged by brake shoes 55 that are carried at the lower ends of levers 51, the upper ends of which are pivotally attached to an arm 58 extending outwardly from the side wall 59. A spring H is provided between adjusting screws 12 and 13 that are attached to the vertical arms or levers 51 to permit applying a desired brake shoe pressure to the brake drum 55.

As best shown in Fig. 5, the outer end of the control shaft 53 is reduced in diameter as shown at 14' providing a shoulder 15. A friction disk 15 is keyed to the shaft as shown at 11 and is biased by a spring 18, engaging the friction disk 15 and an outer disk 19 held in place on the end of the control shaft 53 by a nut 8|. A screw member 82 is loosely mounted about the reduced portion 14 of the control shaft and provided with external screw threads 83 that are adapted to engage internal screw threads 84 of a nut member 85. Disk members 85 and 81 are provided at the opposite ends of the screw member 82 and outer friction disk members 88 and 89 are also rovided for engaging the shoulder 15 and the friction disk 15, respectively. The several members, including disks 88, 85. the screw member 52, disks 91 and 89, are held together as a unit by means of screw 9|, and this unit is biased to rotate in the one or the other direction with the rotation of the control shaft 53 through operation of a friction clutch comprising the shoulder 15 and friction disk 16 that are biased toward each other by the spring 18 on the opposite ends of the assembly, including the screw member 82 and the disks 88, 88, 81 and 89.

A contact arm or switch arm 92 is attached to the nut member 85 and extends downwardly therefrom, the lower end of the arm being positioned between guide blocks 93 when the nut 85 is in its central position, midway of its range of travel between the disks 85 and 81. A switch operating member 99 is carried by the arm 92 as shown on Figs. 4 and 5 and is adapted to engage the leaf spring members 94 or 95 for operating the pairs of switch contact members 4| or 54 into circuit closing positions. The leaf spring members 94 and 95, together with their associated contact members 4| and 54 are mounted on blocks of insulating material 95 and 91 by suitable screw members 98 and 99. The insulating blocks 98 and 91 are recessed to provide space for the guide blocks 93 through which stop screws I9I are positioned, the outer ends I82 of which are adapted to receive the lower end of the switch arm 92 upon movement of this arm in a switch contact members 4| or 54.

Arms I03 are shown extending from the nut member 85 and are biased by springs I84, the lower ends of which are attached to studs I05 mounted in the insulating blocks 95 and 91, respectively. The balancing springs I04 tend to move the nut member 85 from its extreme end and 5, a directional direction to close the anaecee position between the disks 86 and 81, in which position both of the pairs of switch contactmembers M and it are separated. When the motor of the guide block 93 against which it is biased,

and will move in the appropriate direction to engage eitherthe leaf spring 96 or 95 and the stop it: to close one of the pairs or switch contact members II or 54, depending upon the direction in which the shaft and screw member 82 are operated. As the nut 85 is moved in the one or in the other direction along the axis of the screw member 82, projections Ho shown in Fig. 2 ex tending outwardly from the sides of the nut memher will engage similar projections HI on the disk members 86 or 81, preventing further rotation of the screw member 82 which would cause the screw threads to jam. A certain pressure is the direction of rotation of the control shaft 63 to maintain the appropriate pair of switch contact members 4i and to a complete stop and tends to operate in the reverse direction clue to the plugcircuit, the screw assembly and the switch arm 92 tend to operate in the reverse direction. However, immediately upon the start of the mo tor in the reverse direction the plugging circuit is interrupted through the contact members at or thus preventing appreciable movement of the tor in the reverse direction and again bringing' the switch contact arm 952' and, the nut member to their mid or illustrated positions, this operation being aided by the springs Hit,

It will be obvious to one skilled in the art that many modifications of the details of construction illustrated and described may be made within the spirit of the invention and I do not wish to be limited otherwise than by the scope of the appended claims.

I claim as my invention:

2. A directional switch device comprising a operable in either of two directions or rota- 'on, two pairs of switch contact members, and means operable upon. the rotation of the shaft in the one or the other direction of rotation tor closine the one or the other 015 said pairs of switch contact members, and for retaining the contact members closed so long as the shaft continues to rotate in the given direction and to separate the contact members when the shaft stops rotating, said means comprising a screw member having external screw threads thereon,

- of travel,

a nut member having internal screw threads engaging the threads of said screw member and the axis of the screw member in the one or the other direction within a predetermined range of travel, means operable by said out uponapproach to either end of its of said. pairs of switch contacts, a friction clutch for biasing said screw member to rotate in the one or theother direction in accordance with the direction or rotation of the shaft and adapted to slip when the nut member reaches the end of its range of travel in either direction.

2. In a motor in either direction, said preswitch device including two to the movement of the nut in the one direction for presetting screw member and arranged to travel along the axis of the screw member in the one or the other direction within a predetermined range, a friction clutch for biasing said screw member to rotats in the one or the other direction in accordance with the direction of rotation of the shaft and adapted to slip when the nut member reaches the end or its range or" travel in either direction, a pair of: switches, a switch arm operatively attached; to the nut member and positioned between said pair of switches, a pair of guide blocks positioned; on opposite sides of the switch arm when the nut is in the rnidposition of its travel along the screw member for limiting the rotation of the nut member position, said switch arm being operable linearly with the nut member from its midposition upon rotation of the screw member, the guide blocks arranged to permit lateral movement of the switch arm for operating the one or the other of said switches to a circuit closing position upon travel of the nut member to the end oi its range and means operable upon completion an operation of the directional switch device for returning the nut member and switch arm to a position to eflect the return of said switch. to a circuit opening position.

at. directional switch device comprising a shaft operable in either of two directions of ro i one or the other direction tation, two pairs of switch Contact members, and means operable upon the rotation of the shaft in the one or the other direction of rotation for closing the one or the other of said pairs of switch contact members, said means comprising a screw member having external screw threads thereon, a nut member having internal screw threads engaging the threads of said screw member and arranged to travel along the axis of the screw member in the one or the other direction within a predetermined range of travel, a switch arm operable by said nut in the direction of the axis of the shaft and about the axis, and effective upon movement about the axis of the shaft for clos-- ing the one or the other of said pairs of contacts, guide blocks positioned on opposite sides of the switch arm when the nut is in the midposition of its range of travel along the axis of the shaft to prevent operation of the switch contact members, said guide blocks being of a length to prevent operation of the switch arm for closing a pair of contacts until movement of the nut member adjacent the end of its range of travel in the direction of the axis of the shaft, a friction clutch for biasing said screw member to rotate in the in accordance with the direction of rotation of the shaft, said clutch being adapted to slip when. the nut member reaches the end of its range of travel in the direction of its axis in either direction.

5. In a motor driven electrical apparatus, in combination, a motor, a pair of directional. relays for controlling the operation of the motor in the one or the other of two directions of rotation, a preset motor plugging switch device comprising a screw member having external screw threads thereon, a nut member having internal screw threads engaging the threads oi the screw member and arranged to travel along the axis of the screw member in the one or the other direction within a predetermined range, a friction clutch for biasing said screw member comprising frictional members attached to rotate with the shaft on opposite sides of the screw member, resilient means for biasing said friction members toward each other to transmit a frictional torque toward each other to transmit a frictional torque between the friction members and the screw member for biasing the screw member to rotate in the one or the other direction inv accordance with the direction of rotation of the shaft and adapted to slip when the nut member reaches the end or its range of travel in either direction, said preset motor plugging switch device including two switches responsive to the movement of the nut member in the one or the other direction for presetting the one or ging circuits, and means responsive to the moremerit of a directional relay to a motor interru tibing position to complete the plugging circuit, said preset switch device being effective upon the stopping of the rotation of the shaft to interrupt said plugging circuit.

6. In a directional switch device comprising a shaft operable in either of two directions of rotation, a screw member having; external screw threads thereon, a nut member having internal screw threads meshing with the threads of the screw member and arranged to travel along the axis of the screw member in the one or the other direction within a predeterrriihed range, a friction clutch for biasing said screw member comprising friction members keyed to the shaft on opposite sides of the screw member, resilient means, for biasing said friction members toward the other of t'vgo preset plugiii) iii)

the nut member and each other to transmit a frictional torque between the friction members and the screw member for biasing the screw member to rotate in the one or the other direction in accordance with the direction of rotation of the shaft, a pair of switches, a switch arm operatively attached to positioned between said pair of switches, a pair of guide blocks positioned on opposite sides of the switch arm when the nut is in the midpositlon of its travel along the screw member for limiting the'rotation of the nut membet and switch arm to prevent the operation of said pair of switches by said switch arm when the nut member is in its midposition, said switch arm being operable linearly with the nut member from its midposition upon rotation of the screw member, the guide blocks being arranged to permit lateral movement of the switch arm for operating the one or the other of said switches to a circuit closing position upon travel of the nut member to the end of its range of travel, and means for coupling the nut andscrew membars to prevent relative rotation of the two members beyond a predetermined range of movement required for effecting operation of one of said switches.

'7. A directional switch device comprising a shaft operable in either of two directions of rotation, a screw member having external screw threads thereon, a nut member having internal screw threads meshing with the threads of the screw member and arranged to travel along the axis of the screw member in the one Or the other direction within a predetermined range, a friction clutch for biasing said screw member comprising friction members attached to rotate with the shaft on opposite sides of the screw member, resilient means for biasing said friction members toward each other to transmit a frictional torque between the friction members and the screw member for biasing the screw member to rotate in. the one or the other direction in accordance with the direction of rotation of the shaft and adapted, to slip when the nut member reaches the end of its range oi! travel in either direction, a pair of switches, a switch arm operatively attached to the nut member and positioned between said pair of switches, a pair of guide blocks positioned on opposite sides of the switch arm when the nut is in the midposition of its travel along the screw member for limiting the rotation of the nut member and switch arm to prevent the operation of said pair of switches by said switch arm. when the nut member is in its midposition,

- said switch arm being operable linearly with the nut member from its midposition upon rotation of the screw member, the guide blocks being arranged to permit lateral movement of the switch arm for operating the one or the other of said switches to a circuit closing position upon travel of the nut member to the end of its range of travel, and means operable upon completion of an operation of the directional switch device for returning the nut member and switch arm to their midposition to efiect the return of said switch to a circuit opening position.

EDMUND W. KUHN.

REFERENCES CITED UNITED STATES PATENTS Name Watson Number Date NOV. 16, 1926 

